a b s t r a c tAlterations in the levels of molecules which interact with the extracellular matrix, such as integrins, are associated with invasion of oral squamous cell carcinomas (OSCC). The molecular mechanisms underlying dysregulation of integrin expression in OSCC, however, remain unclear. Here, we show that microRNA-124, a small non-coding RNA down-regulated in OSCC, is able to downregulate expression of integrin beta-1 (ITGB1) by interacting with its 3 0 untranslated region. Over-expression of miR-124 attenuates endogenous ITGB1 expression and reduces the adherence and motility of OSCC cells, suggesting disruption of miR-124-mediated repression of ITGB1 may be a key factor in OSCC progression.

The invasion and migration of cancer cells is increasingly recognised to be influenced by factors derived from adjacent tumour-associated stroma. The contextual signals regulating stromal-tumour interactions, however, remain poorly understood. Here, we identify a role for endothelin-1 (ET-1), a mitogenic peptide elevated in a number of malignancies, in promoting pro-metastatic cross-talk between head and neck cancer cells and adjacent fibroblasts. We demonstrate that treatment of oral fibroblasts with ET-1 activates ADAM17-mediated release of epidermal growth factor receptor (EGFR) ligands, triggering EGFR signalling and increased motility in neighbouring head and neck cancer cells. ET-1-mediated paracrine transactivation of EGFR also increased cyclo-oxygenase-2 levels in the cancer cells, providing a molecular insight into the mechanisms by which the elevated levels of ET-1 observed in head and neck cancers may contribute to disease progression.It is increasingly apparent that cancer cell migration, invasion and subsequent metastasis are the result of complex interactions between the epithelial tumour cells and the surrounding stroma. 1 Within the tumour-associated stroma, a variety of different cell types are thought to provide contextual signals which promote cancer cell motility, including endothelial cells, inflammatory cells and fibroblasts. 2 Of these, fibroblasts are the most numerous and play a critical role in maintaining homeostasis of the extracellular matrix (ECM). 3 It is proposed that within tumour-associated stroma, fibroblasts become aberrantly activated and contribute to tumour invasion by modifying the ECM and secreting factors which promote cancer cell motility. 3 The factors promoting tumourstromal interactions, however, remain to be fully elucidated.Head and neck cancer (predominantly comprising head and neck squamous cell carcinomas, HNSCC) is the sixth most common cancer worldwide and is increasing in prevalence. It carries a poor prognosis and survival rates have improved little over the last three decades. 4 In comparison with other common cancers, the mechanisms underlying the progression of head and neck cancer are poorly understood, hampering the development of novel therapeutic strategies. The motility of head and neck cancer cells is known to be influenced by soluble factors that bind to specific G-protein coupled receptors (GPCRs) such as bradykinin (BK) 5 and gastrin releasing peptide. 6 These act in an autocrine manner, directly binding to receptors on cancer cells to promote invasion and migration by transactivating epidermal growth factor receptor (EGFR) signalling. 5 EGFR signalling is an important regulator of cellular processes such as proliferation, differentiation, apoptosis and migration. 7 Aberrant EGFR activation is found in a wide variety of malignancies, including HNSCC, resulting from mutation, overexpression or the elevation of local levels of soluble ligands such as TGFa, amphiregulin and HB-EGF. 7 Binding of these ligands induces dimerisation and autophosphorylat...

The dissemination of cancer cells to local and distant sites depends on a complex and poorly understood interplay between malignant cells and the cellular and non-cellular components surrounding them, collectively termed the tumour microenvironment. One of the most abundant cell types of the tumour microenvironment is the fibroblast, which becomes corrupted by locally derived cues such as TGF-β1 and acquires an altered, heterogeneous phenotype (cancer-associated fibroblasts, CAF) supportive of tumour cell invasion and metastasis. Efforts to develop new treatments targeting the tumour mesenchyme are hampered by a poor understanding of the mechanisms underlying the development of CAF. Here, we examine the contribution of microRNA to the development of experimentally-derived CAF and correlate this with changes observed in CAF derived from tumours. Exposure of primary normal human fibroblasts to TGF-β1 resulted in the acquisition of a myofibroblastic CAF-like phenotype. This was associated with increased expression of miR-145, a miRNA predicted in silico to target multiple components of the TGF-β signalling pathway. miR-145 was also overexpressed in CAF derived from oral cancers. Overexpression of miR-145 blocked TGF-β1-induced myofibroblastic differentiation and reverted CAF towards a normal fibroblast phenotype. We conclude that miR-145 is a key regulator of the CAF phenotype, acting in a negative feedback loop to dampen acquisition of myofibroblastic traits, a key feature of CAF associated with poor disease outcome.

Angiotensin II (Ang II) is the product of the proteolytic action of angiotensin-converting enzyme (ACE) on the precursor peptide, angiotensin I (Ang I). In addition to its vasoactive properties, Ang II is able to stimulate angiogenesis and act as a mitogen, promoting cellular proliferation. Recently, evidence has emerged that Ang II is also able to promote tumour invasion, a key step in the metastatic cascade, although the mechanisms by which it does so remain largely obscure. Here we show that Ang II is able to promote the invasion and migration of head and neck squamous cell carcinoma (HNSCC) cells both in an autocrine manner and by triggering stromal tumour-paracrine interactions. The effects of Ang II on autocrine and paracrine signalling pathways are mediated by angiotensin receptor 1 (AT R) and inhibited by angiotensin 1-7 (Ang 1-7), a peptide produced from Ang II by the action of angiotensin-converting enzyme 2 (ACE2). These data are the first to demonstrate a role for the renin-angiotensin system in oral carcinogenesis and raise the possibility of utilizing AT R receptor antagonists and/or Ang 1-7 as novel therapeutic agents for HNSCC.

In oral squamous cell carcinoma, a frequently fatal and increasingly common epithelial malignancy of the oral cavity, ET-1 is known to contribute to pro-migratory paracrine signalling between stromal fibroblasts and cancer cells. The ability of ET-1 to modulate the phenotype of human oral stromal fibroblasts, however, has not previously been reported. The findings presented here suggest that targeting the stromal endothelin system may be a viable and novel therapeutic strategy for invasive oral cancer.